In U.S. Pat. No. 5,448,582, issued Sep. 5, 1995, entitled "Optical Sources Having a Strongly Scattering Gain Medium Providing Laser-Like Action", the inventor disclosed a multi-phase gain medium including an emission phase (such as dye molecules) and a scattering phase (such as TiO.sub.2). A third, matrix phase may also be provided in some embodiments. Suitable materials for the matrix phase include solvents, glasses and polymers. The gain medium is shown to provide a laser-like spectral linewidth collapse above a certain pump pulse energy. The gain medium is disclosed to be suitable for encoding objects with multiple-wavelength codes, and to be suitable for use with a number of substrate materials, including polymers and textiles.
A problem exists in the field of sorting garments and textiles, such as rented work uniforms, sheets, towels, surgical covers and wraps, and similar materials. For example, it may be desirable to mass wash and press a large number of rented shirts, and then to sort the shirts for delivery to a number of different customers. If the shirts are marked with a customer-identifying indicia, such as lettering and/or a bar code, using an ink, after several washings the indicia may become unreadable to human or optically based scanners. Also, it may be difficult to properly align the indicia with an optical reader, thus impairing the recognition accuracy. This is especially true when the garments are moving relative to the scanner, such as when they are attached to a moving rail or placed on a conveyor belt. In such an application an output of the reader, such as a bar code scanner, can be used to operate a mechanical diverter, so as to route the sorted garments to different locations. If the recognition accuracy is not optimum the end result is incorrectly sorted garments.
This problem is even more pronounced if soiled garments or textiles are to be scanned, sorted and/or accounted for when returned by customers. The presence of dirt, grease, and other materials may obscure the indicia, making accurate recognition even more problematical.